Phosphogypsum-based vegetation concrete and use method thereof

Abstract

The invention discloses ardealite-based vegetation concrete and a use method thereof.The ardealite-based vegetation concrete is prepared from, by mass, 40%-50% of sand clay, 15%-20% of organic nutrient soil, 15%-20% of ardealite, 1.5%-2.5% of cement, 0.2%-0.5% of a water-retaining agent, 0.15%-0.20% of a microbial agent and the balance water; the use method is three-stage spray seeding, standing needs to be conducted for 15-30 min after spray seeding is completed each time, and herbal seeds and shrub seeds are added into the ardealite-based vegetation concrete during spray seeding in the third stage. According to the method, a large amount of ardealite is consumed, the coverage rate of plant communities is increased, and rapid restoration of the side slope is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of resource utilization of phosphogypsum, and particularly relates to a phosphogypsum-based vegetation concrete and a using method thereof. Background Art

[0002] Phosphogypsum is a by-product in the production process of wet-process phosphoric acid. Its main component is calcium sulfate dihydrate, which is an important renewable gypsum resource. In recent years, nearly 50 million tons of newly piled phosphogypsum are added in China every year, and the total piled amount exceeds 300 million tons. However, the main method for treating phosphogypsum in China at present is stacking. The stacking of a large amount of phosphogypsum not only occupies a large amount of land, but also pollutes underground water sources, soil and the atmosphere after long-term stacking, damaging the surrounding ecological environment, which hinders the sustainable development of the phosphorus chemical industry. Therefore, how to promote the reduction and resource utilization of phosphogypsum has become an urgent problem to be solved.

[0003] At present, the comprehensive utilization ways of phosphogypsum mainly include the preparation of building materials such as high-strength hemihydrate gypsum and cement retarder, the recycling of sulfur-calcium resources such as the production of sulfuric acid and co-production of cement, potassium sulfate, ammonium sulfate, etc. from phosphogypsum, and the use in agricultural fields such as soil conditioner and sulfur-calcium-silicon fertilizer. With the acceleration of the urbanization process and the continuous expansion of infrastructure construction, slope protection projects play an important role in flood control, drainage, landscape beautification, etc. Traditional concrete slope protection materials, such as cement concrete, although have high strength and durability, but their ecological properties are poor, which is not conducive to the growth of vegetation and the protection of the ecological environment. Therefore, it is considered to introduce phosphogypsum to modify the vegetation concrete slope protection materials to improve the mechanical properties, durability and vegetation growth performance of the vegetation concrete.

[0004] Chinese Patent CN116120030A discloses a solid waste recycled vegetation concrete cementitious material, which includes portland cement, modified phosphogypsum, volcanic ash, perlite, tailings, polyacrylamide, potassium sulfate and ammonium sulfate. The modified phosphogypsum is prepared by washing and drying 40-60 parts of phosphogypsum until the water content is less than 0.5%, and then adding 1-3 parts of water-absorbing resin and 2-5 parts of humic acid and grinding to a specific surface area greater than 650m 2 / kg. The cementitious material provided by this invention has low carbon emissions, low original pH value, less buffer agent dosage, simple curing conditions, high seed germination rate and good slope protection effect.

[0005] Chinese Patent CN115977119A discloses a design method for a phosphogypsum highway subgrade protection project, including: leveling and compacting the slope surface of the completed phosphogypsum subgrade; spraying a mixture of sodium silicate and calcium chloride on the slope surface to seal the rainwater infiltration channel into the subgrade and improve the strength and frost resistance of the phosphogypsum subgrade; making a concrete frame beam and a drainage ditch on the slope, and then filling the frame with cohesive soil, sowing grass seeds and / or low shrub tree species with developed roots to stabilize the slope of the phosphogypsum subgrade and meet the requirements of greening and water sealing.

[0006] However, when using phosphogypsum materials for slope protection at present, only the strength of the slope protection materials and the germination rate of plant seeds are generally considered. However, plants often need to form a rich plant community and have a high coverage rate to have a stable and long-term slope protection ability and further resist heavy rain erosion under high strength. Summary of the Invention

[0007] In view of the above technical problems, the present invention provides a phosphogypsum-based vegetation concrete and its use method, which consumes a large amount of phosphogypsum, improves the coverage rate of the plant community, and realizes the rapid repair of the slope.

[0008] To achieve the above object, the present invention provides a phosphogypsum-based vegetation concrete, which includes the following raw materials by mass percentage: 40-50% of sandy clay, 15-20% of organic nutrient soil, 15-20% of phosphogypsum, 1.5-2.5% of cement, 0.2-0.5% of water retaining agent, 0.15-0.20‰ of microbial inoculum, and the balance is water.

[0009] Preferably, the pH value of the sandy clay is 6-8, 17>lp≥10, 0.25<IL≤0.75.

[0010] Preferably, the organic nutrient soil is composed of peat, humus soil, and leaf mold soil in a mass ratio of 1-3:1:4:1-2.

[0011] More preferably, the pH value of the organic nutrient soil is 6-8, the total organic matter content is 30-50%, and the total content of nitrogen, phosphorus, and potassium is 3-8%.

[0012] Preferably, the phosphogypsum is dihydrate phosphogypsum, the pH value is 4-6, the content of dihydrate calcium sulfate is 80-95%, and the particle size is 5-50μm.

[0013] Preferably, the cement is Portland cement, and the specific surface area is 430-500m 2 / kg.

[0014] Preferably, the water retaining agent is composed of polyacrylamide, cellulose, and protein in a mass ratio of 1-6:1-3:1-3.

[0015] More preferably, the cellulose is one or more of hydroxymethylated cellulose, hydroxypropylated cellulose and xanthated cellulose; the protein is one or more of soy protein, gluten and silk protein.

[0016] More preferably, the particle size of the water retaining agent is 20-40 mesh Preferably, the microbial inoculant is a mass ratio mixture of rhizobium inoculant, nitrogen-fixing bacteria inoculant, silicate microorganism inoculant and growth-promoting bacteria inoculant.

[0017] More preferably, the effective viable bacteria concentration of the rhizobium inoculant is (20-80)×10 8 cfu / kg, the effective viable bacteria concentration of the nitrogen-fixing bacteria inoculant is (10-50)×10 8 cfu / kg, the effective viable bacteria concentration of the silicate microorganism inoculant is (15-30)×10 8 cfu / kg, the effective viable bacteria concentration of the growth-promoting bacteria inoculant is (5-20)×10 8 cfu / kg.

[0018] Even more preferably, the rhizobium inoculant is a soybean rhizobium inoculant or / and an alfalfa rhizobium inoculant; the nitrogen-fixing bacteria inoculant is a nitrogen-fixing bacillus inoculant or / and a brown ball nitrogen-fixing bacteria inoculant; the silicate microorganism inoculant is a mucilaginous bacillus inoculant or / and a circular bacillus inoculant; the growth-promoting bacteria inoculant is a pseudomonas fluorescens inoculant.

[0019] Even more preferably, the dosage form of the inoculant is liquid or solid.

[0020] The present invention also provides a method for using the phosphogypsum-based vegetation concrete, including the following steps: (1) Level the slope from March to September, drill holes, install anchor bolts and then hang a net; (2) Mix sandy clay, organic nutrient soil, phosphogypsum, cement, water retaining agent and microbial inoculant to obtain a spraying substrate; (3) Thoroughly wet the slope surface, place the spraying substrate in a soil spraying machine, adjust the distance between the nozzle and the slope surface to 6-8 m, and the spraying angle to 40-50°, and spray in three stages: The first stage: Spray the substrate on the front, with a thickness of 4-5 cm, and let it stand for 15-30 min after spraying; The second stage: Spray the substrate on the front, with a thickness of 4-5 cm, and let it stand for 15-25 min after spraying; The third stage: Mix the spraying substrate with plant seeds, spray on the front, with a thickness of 1.5-3.0 cm, and let it stand for 20-25 min after spraying; (4)The cover is used to protect until the plants grow to 5 - 6 cm, and atomized water spraying is used for maintenance until the plants completely cover the slope surface.

[0021] Preferably, after the slope is leveled in step (1), the unevenness is on average ±15 cm, and the maximum does not exceed 30 cm.

[0022] Preferably, in step (1), the spacing of the anchor rods is 1 m × 1 m; the mesh is a galvanized iron wire mesh, adjacent meshes are connected with iron wires or nylon, and the distance between the mesh surface and the slope surface is 5 - 10 cm.

[0023] Preferably, in the third stage of step (3), after the spraying substrate is mixed with the plant seeds, the seeding rate of the plant seeds per square meter is 20 - 30 g.

[0024] More preferably, the plant seeds are multiple of tall fescue, ryegrass, bahiagrass, bermudagrass, Amorpha fruticosa and Indigofera amblyantha, and the plant seeds are soaked in warm water at 25 - 30 °C for 6 - 10 h for germination treatment before mixed spraying.

[0025] Even more preferably, the herbs in the plant seeds account for 5 - 6%, and the shrubs account for 94 - 95%.

[0026] Preferably, the cover in step (4) is a non-woven fabric or plastic film of 25 - 30 g / m 2 ; when atomized water spraying is used for maintenance, the water content of the slope surface is ensured to be 60 - 70%.

[0027] The beneficial effects of the present invention are as follows: 1. Vegetation concrete is prepared by using phosphogypsum and can be used for slope protection. The phosphorus, sulfur, calcium, silicon and other nutrient components rich in phosphogypsum can promote the growth of plants, and at the same time make the slope have good water permeability and air permeability, enhance the soil alkali resistance, and the strength can still reach more than 0.38 MPa under the premise of reducing 50% of the cement dosage, with good anti-scouring ability, and improve the resistance of the slope to rainstorm scouring.

[0028] 2. A water retaining agent is obtained by compounding polyacrylamide with cellulose and protein, which can improve the saturated water content of the soil with less dosage, increase the proportion of water easily available to vegetation by 36.47%, and further improve the growth of plants.

[0029] 3. A variety of microbial inoculants are mixed and incorporated into the phosphogypsum-based vegetation concrete, which improves the chemical environment of the vegetation concrete, enhances the biochemical activity, fertilizer utilization rate and use effect, and finally promotes plants to absorb the nutrient components in the phosphogypsum, promotes growth, and realizes the purpose of sustainable fertility of the prepared concrete.

[0030] 4. Select appropriate plant seeds and use the method of mixed seeding of shrubs and grasses to quickly establish a plant community with high coverage. In the early stage, tall fescue grows rapidly and has high adaptability, enabling the rapid revegetation of the slope. In the later stage, Amorpha fruticosa has well-developed roots, improving the slope stability performance, quickly achieving slope restoration, and enhancing the resistance of the slope. Description of the Drawings

[0031] Figure 1 It is a bar chart showing the effect of phosphogypsum content on the above-ground biomass of plants.

[0032] Figure 2 It is the effect of phosphogypsum on the germination rate of tall fescue seeds. In the figure, A is Comparative Example 1, B is Comparative Example 2, and C is Example 1.

[0033] Figure 3 The effect of phosphogypsum-based vegetation concrete with different formulations in Example 6 on the growth of tall fescue. In the figure, A is Example 2 and B is Comparative Example 4.

[0034] Figure 4 It is a diagram showing the coverage rate of different plants planted in the phosphogypsum-based vegetation concrete prepared in Example 2. In the figure, A is tall fescue, B is Amorpha fruticosa, C is bermudagrass, and D is perennial ryegrass.

[0035] Figure 5 It is the slope restoration situation of Example 7. Detailed Embodiments

[0036] The technical solutions of the present invention will be further explained and illustrated below in conjunction with the drawings and specific embodiments. It should be noted that the following embodiments are only the preferred embodiments of the present invention and should not be construed as a limitation of the present invention. The protection scope of the present invention should be determined by the content recorded in the claims. Modifications and substitutions made by those skilled in the art to the technical solutions of the present invention without creative efforts fall within the protection scope of the present invention.

[0037] Dihydrate phosphogypsum: The crystal water content is 23.7%, the particle size is 5 - 50 μm, and the main components are shown in the following table:

[0038] Example 1 A phosphogypsum-based vegetation concrete, by mass percentage, includes 40% sandy clay, 15% organic nutrient soil, 20% dihydrate phosphogypsum, 1.5% Portland cement (specific surface area is 450 m 2 / kg), 0.2% water-retaining agent, 0.15‰ microbial inoculant, and the balance is water; Among them, the organic nutrient soil is composed of peat soil, humus soil, and leaf mold soil in a mass ratio of 1:1:1; The water-retaining agent (20 mesh) is composed of polyacrylamide, xanthated cellulose, and soy protein in a mass ratio of 1:1:1; The microbial inoculant is composed of Bradyrhizobium japonicum inoculant (effective viable bacteria concentration is 20×10 8 cfu / kg), Azotobacter chroococcum inoculant (effective viable bacteria concentration is 10×10 8 cfu / kg), Bacillus mucilaginosus (effective viable bacteria concentration is 15×10 8 cfu / kg), and Pseudomonas fluorescens inoculant (effective viable bacteria concentration is 5×10 8 cfu / kg); The preparation method is as follows: (1) Prepare organic nutrient soil, water-retaining agent, and microbial inoculant; (2) Stir and mix sandy clay, organic nutrient soil, dihydrate phosphogypsum, portland cement, and water-retaining agent to obtain a mixed material; (3) Dissolve the microbial inoculant in water to obtain an aqueous solution; (4) Add the aqueous solution to the mixed material and stir evenly to obtain phosphogypsum-based vegetation concrete.

[0039] Example 2 A phosphogypsum-based vegetation concrete, by mass percentage, includes 45% sandy clay, 18% organic nutrient soil, 18% dihydrate phosphogypsum, 2.0% portland cement (specific surface area is 480 m 2 / kg), 0.4% water-retaining agent, 0.18‰ microbial inoculant, and the balance is water; Among them, the organic nutrient soil is composed of peat soil, humus soil, and leaf mold soil in a mass ratio of 2:3:2; The water-retaining agent (20 mesh) is composed of polyacrylamide, hydroxypropylated cellulose, and gluten in a mass ratio of 6:1:2; The microbial inoculant is composed of Bradyrhizobium japonicum inoculant (effective viable bacteria concentration is 50×10 8 cfu / kg), Azotobacter chroococcum inoculant (effective viable bacteria concentration is 30×10 8 cfu / kg), Bacillus mucilaginosus (effective viable bacteria concentration is 25×10 8 cfu / kg), and Pseudomonas fluorescens inoculant (effective viable bacteria concentration is 15×10 8 cfu / kg) and are mixed in equal mass; The preparation method is the same as that in Example 1.

[0040] Example 3 A phosphogypsum-based vegetation concrete, by mass percentage, includes 50% sandy clay, 20% organic nutrient soil, 15% dihydrate phosphogypsum, portland cement (specific surface area is 500 m 22.5% by mass of water-retaining agent, 0.5% of water-retaining agent, 0.20‰ of microbial inoculum, and the balance is water; Among them, the organic nutrient soil is composed of peat soil, humus soil and leaf mold soil in a mass ratio of 1:4:1; The water-retaining agent (20 mesh) is composed of polyacrylamide, hydroxymethylated cellulose and silk protein in a mass ratio of 4:3:3; The microbial inoculum consists of alfalfa rhizobium inoculum (effective viable bacteria concentration of 80×10 8 cfu / kg), nitrogen-fixing bacillus inoculum (effective viable bacteria concentration of 50×10 8 cfu / kg), circular bacillus inoculum (effective viable bacteria concentration of 30×10 8 cfu / kg) and Pseudomonas fluorescens inoculum (effective viable bacteria concentration of 20×10 8 cfu / kg) and other mass mixtures; The preparation method is the same as that of Example 1.

[0041] Example 4 A phosphogypsum-based vegetation concrete, by mass percentage, includes 42% of sandy clay, 20% of organic nutrient soil, 18% of dihydrate phosphogypsum, Portland cement (specific surface area of 480 m 2 / kg) 2.3%, water-retaining agent 0.4%, microbial inoculum 0.15‰, and the balance is water; Among them, the organic nutrient soil is composed of peat soil, humus soil and leaf mold soil in a mass ratio of 3:4:2; The water-retaining agent (20 mesh) is composed of polyacrylamide, hydroxypropyl cellulose and gluten in a mass ratio of 2:1:1; The microbial inoculum consists of soybean rhizobium inoculum (effective viable bacteria concentration of 40×10 8 cfu / kg), alfalfa rhizobium inoculum (effective viable bacteria concentration of 40×10 8 cfu / kg), brown ball nitrogen-fixing bacteria inoculum (effective viable bacteria concentration of 20×10 8 cfu / kg), nitrogen-fixing bacillus inoculum (effective viable bacteria concentration of 20×10 8 cfu / kg), Bacillus mucilaginosus (effective viable bacteria concentration of 15×10 8 cfu / kg), circular bacillus inoculum (effective viable bacteria concentration of 15×10 8 cfu / kg) and Pseudomonas fluorescens inoculum (effective viable bacteria concentration of 15×10 8 cfu / kg) and other mass mixtures; The preparation method is the same as that of Example 1.

[0042] Example 5 A phosphogypsum-based vegetation concrete, by mass percentage, includes 45% of sandy clay, 15% of organic nutrient soil, 20% of dihydrate phosphogypsum, 1.6% of portland cement (specific surface area is 480 m 2 / kg), 0.3% of water-retaining agent, 0.16‰ of microbial inoculant, and the balance is water; Among them, the organic nutrient soil is composed of peat soil, humus soil and leaf mold soil according to the mass ratio of 2:3:2; The water-retaining agent (20 mesh) is composed of polyacrylamide, cellulose and protein according to the mass ratio of 6:1:2; among them, the cellulose is composed of hydroxymethylated cellulose and hydroxypropylated cellulose in equal mass ratio, and the protein is composed of soy protein, gluten and sericin in equal mass ratio; The microbial inoculant is composed of soybean rhizobium inoculant (effective viable bacteria concentration is 50×10 8 cfu / kg), brown nitrogen-fixing bacteria inoculant (effective viable bacteria concentration is 30×10 8 cfu / kg), Bacillus mucilaginosus (effective viable bacteria concentration is 25×10 8 cfu / kg) and Pseudomonas fluorescens inoculant (effective viable bacteria concentration is 15×10 8 cfu / kg) in equal mass; The preparation method is the same as that of Example 1.

[0043] Comparative Example 1 The method and steps are the same as those of Example 1, only replacing all phosphogypsum with sandy clay to prepare the vegetation concrete.

[0044] Comparative Example 2 The method and steps are the same as those of Example 1, only replacing phosphogypsum with phosphogypsum particles of 40-100 mesh to prepare the phosphogypsum-based vegetation concrete.

[0045] Comparative Example 3 (1) The method and steps are the same as those of Example 1, changing the dosage of phosphogypsum to 5%, 10%, 25%, 30%, 35%, 40%, 45%, 50%, 55% and 60% respectively, and changing the dosage of sandy clay to 50% to prepare the phosphogypsum-based vegetation concrete; (2) Mix the phosphogypsum-based vegetation concrete prepared in step (1) with the phosphogypsum-based vegetation concrete prepared in Example 1, Example 3 and Comparative Example 1 and tall fescue seeds according to the mass ratio of 2500:1, place them in a planting pot with a thickness of 2 cm, and normally cure for 20 days, and count the above-ground biomass of tall fescue. The results are shown in Figure 1 ; (3) Take the phosphogypsum-based vegetation concrete prepared in step (1) and the phosphogypsum-based vegetation concretes prepared in Example 1, Example 3 and Comparative Example 1 for unconfined compressive strength testing. The results are shown in Table 1. When the phosphogypsum content is 15% - 25%, the strength can reach above 0.40 MPa, with good anti-scouring ability, improving the resistance of the slope to rainstorm scouring.

[0046] The results are as Figure 1 shown. With the increase of the phosphogypsum content, the above-ground biomass of tall fescue shows a trend of increasing first and then decreasing gradually. Among them, when the phosphogypsum content is 10% - 50%, the above-ground biomass of tall fescue is relatively high. When the phosphogypsum content is 40%, the biomass is the highest, which is 1.7 g.

[0047] Table 1 Influence of phosphogypsum content on unconfined compressive strength

[0048] Result detection: Take the vegetation concretes prepared in Example 1 and Comparative Examples 1 - 2, and mix them with tall fescue seeds at a mass ratio of 2500:1. Place them in a planting pot with a thickness of 2 cm and cure normally for 10 days. Count the germination rate of tall fescue. Among them, before mixing with the vegetation concrete, the tall fescue seeds are soaked in warm water at 25°C for 8 h for germination promotion treatment. The results are shown in Table 2 and Figure 2 : Table 2 Germination rate of tall fescue in vegetation concrete

[0049] As can be seen from Table 2 and Figure 2 it can be known that adding phosphogypsum to the vegetation concrete can improve the germination rate of plant seeds. Compared with the relatively large-particle phosphogypsum, the relatively small-particle phosphogypsum powder can only improve the germination rate and growth of plant seeds in the vegetation concrete. In addition, the relatively small-particle phosphogypsum powder does not require additional processing and has low transportation costs, which can further reduce costs.

[0050] Comparative Example 4 The method and steps are the same as those in Example 1, except that all the water-retaining agent is changed to polyacrylamide to prepare the phosphogypsum-based vegetation concrete.

[0051] Comparative Example 5 The method and steps are the same as those in Example 1, except that the water-retaining agent is changed to a composition of hydroxymethylated cellulose and soy protein at a mass ratio of 1:1 to prepare the phosphogypsum-based vegetation concrete.

[0052] Comparative Example 6 The method and steps are the same as those in Example 1, except that the dosage of the water-retaining agent is changed to 0.1% to prepare the phosphogypsum-based vegetation concrete.

[0053] Comparative Example 7 The method and steps were the same as those in Example 1, except that the dosage of the water retaining agent was changed to 0.8%, and phosphogypsum-based vegetation concrete was prepared.

[0054] Example 6 (1) Take the phosphogypsum-based vegetation concrete prepared in Example 2 and Comparative Examples 4-7, mix it with tall fescue seeds at a mass ratio of 2500:1, place it in a planting pot with a thickness of 2 cm, and cure it normally for 10 days. Count the germination rate and growth of tall fescue. Before mixing with the vegetation concrete, the tall fescue seeds were soaked in warm water at 25 °C for 8 h for germination treatment. The results are shown in Table 3 and Figure 3 ; (2) Take the phosphogypsum-based vegetation concrete prepared in Example 2 and Comparative Examples 5-8, and measure its saturated water content by the container method. The results are shown in Table 3; (3) Take the phosphogypsum-based vegetation concrete prepared in Example 2 and Comparative Examples 5-8, and spray it onto the simulated slope (slope ratio 1:1) in batches: First time: Spray the phosphogypsum-based vegetation concrete onto the slope at a 45° angle with a thickness of 8 cm, and let it stand for 20 min after spraying; Second time: Mix the phosphogypsum-based vegetation concrete with tall fescue seeds at a mass ratio of 2500:1, spray it onto the slope at a 45° angle with a thickness of 2 cm, and let it stand for 20 min after spraying; (4) Cure it normally for 50 days after spraying; (5) Simulate the rainfall intensity of 5.0 mm / min (belonging to the rainstorm level), and count the mass of the phosphogypsum-based vegetation concrete washed down (substrate mass). The results are shown in Table 3.

[0055] Table 3 Influence of water retaining agent on the performance of phosphogypsum vegetation concrete

[0056] The results show from Table 3 and Figure 3 It can be seen that the water retaining agent compounded with multiple substances can significantly increase the saturated water content of the vegetation concrete, increase the plant height of tall fescue, and at the same time improve the resistance of the vegetation concrete to rainwater erosion.

[0057] Comparative Example 8 The method and steps were the same as those in Example 1, except that all the microbial inoculants were changed to soybean rhizobium inoculants (effective viable bacteria concentration 20×10 8 cfu / kg), and phosphogypsum-based vegetation concrete was prepared.

[0058] Comparative Example 9 The method and steps were the same as those in Example 1, except that no microbial inoculant was used, and phosphogypsum-based vegetation concrete was prepared.

[0059] Comparative Example 10 The method and steps are the same as those in Example 1, except that the microbial inoculant is changed to be composed of equal mass ratios of soybean rhizobium inoculant (effective viable bacteria concentration is 20×10 8 cfu / kg) and azotobacter chroococcum inoculant (effective viable bacteria concentration is 10×10 8 cfu / kg) to prepare phosphogypsum-based vegetation concrete.

[0060] Comparative Example 11 The method and steps are the same as those in Example 1, except that the microbial inoculant is changed to be composed of equal mass ratios of bacillus mucilaginosus (effective viable bacteria concentration is 15×10 8 cfu / kg) and pseudomonas fluorescens inoculant (effective viable bacteria concentration is 5×10 8 cfu / kg) to prepare phosphogypsum-based vegetation concrete.

[0061] Comparative Example 12 The method and steps are the same as those in Example 1, except that the dosage of the microbial inoculant is changed to 0.25‰ to prepare phosphogypsum-based vegetation concrete.

[0062] Result detection: Take the phosphogypsum-based vegetation concrete prepared in Example 2 and Comparative Examples 8-12, mix it with the high fescue seeds after germination treatment according to a mass ratio of 2500:1, place it in a culture dish, and normally cure for 10 days. Count the germination rate and coverage rate of the plant seeds. The results are shown in Figure 4 ; Take the phosphogypsum-based vegetation concrete prepared in Example 2, mix it with the high fescue, Amorpha fruticosa, and bermudagrass ryegrass seeds after germination treatment according to a mass ratio of 2500:1 respectively, place it in a culture dish, and normally cure for 10 days. Count the germination rate and coverage rate of the plant seeds. The results are shown in Figure 5 and Table 5.

[0063] Table 4 Influence of microbial inoculant on the growth of plant seeds

[0064] Table 5 Growth of different types of plant seeds in phosphogypsum-based vegetation concrete

[0065] The results show that the microbial inoculant composed of multiple inoculants can significantly promote the growth of plants and improve the coverage rate (Table 4). At the same time, high fescue and Amorpha fruticosa in the phosphogypsum-based vegetation concrete can quickly achieve a high coverage rate, accelerating the slope repair process, and the plants with a high coverage rate can further improve the anti-scouring ability of the slope to rainwater.

[0066] Example 7 (1)Select a roadbed slope in a certain place in Yichang City, Hubei Province, with a slope of 65°. Level the slope to remove loose stones and garbage, and ensure that the unevenness of the slope surface is ±15 cm on average, with a maximum of no more than 30 cm. (2)According to the bolt spacing of 1 m × 1 m, use a pneumatic drill to drill holes. The direction of the drill holes is perpendicular to the slope surface, with a hole diameter of 25 mm. Then place the bolts in the drill holes and fix them with cement mortar. (3)From top to bottom, fix the galvanized iron wire mesh on the bolts, with the mesh surface 7 cm away from the slope surface. Connect adjacent rolls of galvanized iron wire mesh with iron wire, and then spray water on the slope surface to make the slope surface fully wet. (4)Prepare the phosphogypsum-based vegetation concrete according to the formula described in Example 2, place it in a soil spraying machine, and then adjust the nozzle of the soil spraying machine to be 7 m away from the slope surface and at an angle of 45° to the slope surface for three-stage spraying: The first stage: Uniformly spray on the front surface to make the thickness of the phosphogypsum-based vegetation concrete 4 cm, and let it stand for 20 min after spraying. The second stage: Uniformly spray on the front surface to make the thickness of the phosphogypsum-based vegetation concrete 4 cm, and let it stand for 20 min after spraying. The third stage: Add plant seeds to the phosphogypsum-based vegetation concrete, mix evenly, and then uniformly spray on the front surface to make the thickness of the phosphogypsum-based vegetation concrete 2 cm. Let it stand for 20 min after spraying. The mass ratio of the phosphogypsum-based vegetation concrete to the plant seeds is 2500:1. The plant seeds are composed of 6% tall fescue and 94% Amorpha fruticosa seeds by mass percentage. The plant seeds are soaked in warm water at 25 °C for 8 h before spraying for germination treatment. (5)After spraying, cover the slope surface with non-woven fabric of 28 g / m² for water retention. When the plant seedlings grow to 5 - 6 cm, remove the covering. Then use a water spraying device to spray the slope surface atomized in small amounts and multiple times for 50 days of maintenance. During the maintenance process, ensure that the water content of the slope surface is within the range of 60 - 70%.

[0067] Six months after the end of maintenance, the slope surface is detected. It is found that the strength of the slope surface is between 0.38 - 0.45 MPa, does not crack or collapse under the rainfall erosion of 120 mm / h, has strong anti-rainstorm erosion ability. In addition, the leaching rate of harmful substances such as heavy metal ions meets the standard, and the coverage rate of the plant community can reach 98%.

Claims

1. A phosphogypsum-based vegetation concrete, characterized in that: According to the mass percentage, the raw materials include: sand and clay 40-50%, organic nutrient soil 15-20%, phosphogypsum 15-20%, cement 1.5-2.5%, water retaining agent 0.2-0.5%, microbial agent 0.15-0.20‰, and the balance is water.

2. The phosphogypsum-based vegetation concrete according to claim 1, characterized in that: The organic nutrient soil is composed of peat, humus and leaf mold in a mass ratio of 1-3:1:4:1-2.

3. The phosphogypsum-based vegetation concrete according to claim 1, characterized in that: The phosphogypsum is dihydrate phosphogypsum, with a pH value of 4-6, a content of dihydrate calcium sulfate of 80-95%, and a particle size of 5-50 μm.

4. The phosphogypsum-based vegetation concrete according to claim 1, characterized in that: The water retaining agent is composed of polyacrylamide, cellulose and protein in a mass ratio of 1-6:1-3:1-3.

5. The phosphogypsum-based vegetation concrete according to claim 4, characterized in that: The cellulose is one or more of hydroxymethyl cellulose, hydroxypropyl cellulose and xanthated cellulose; the protein is one or more of soy protein, gluten and silk protein.

6. The phosphogypsum-based vegetation concrete according to claim 1, characterized in that: The microbial agent is a mixture of rhizobium agents, nitrogen-fixing bacteria agents, silicate microbial agents and growth-promoting agents in equal mass ratios.

7. The phosphogypsum-based vegetation concrete according to claim 6, characterized in that: The effective live bacteria concentration of the rhizobium agent is (20-80)×10 8 cfu / kg, the effective live bacteria concentration of nitrogen-fixing bacteria agent is (10-50)×10 8 cfu / kg, the effective live bacteria concentration of silicate microbial inoculant is (15-30)×10 8 cfu / kg, the effective live bacteria concentration of the growth-promoting agent is (5-20)×10 8 cfu / kg.

8. A method for using phosphogypsum-based vegetation concrete, characterized in that: The steps include: (1) Level the slope, drill holes, install anchor rods and then hang the net; (2) Mixing sandy clay, organic nutrient soil, phosphogypsum, cement, water-retaining agent and microbial agent to obtain a spraying base material; (3) The slope surface is fully wetted with water and sprayed in three stages: The first stage: spray the substrate from the front with a thickness of 4-5cm. After spraying, let it stand for 15-30 minutes; The second stage: spray the substrate from the front with a thickness of 4-5cm. After spraying, let it stand for 15-25 minutes; The third stage: Mix the spraying substrate with the plant seeds, spray them from the front with a thickness of 1.5-3.0cm, and let them stand for 20-25 minutes after spraying; (4) Cover the plants until they grow to 5-6 cm, and spray water until the plants completely cover the slope.

9. The method of use according to claim 8, characterized in that: After the leveling of the slope in step (1), the average convexity and concavity is ±15 cm, and the maximum does not exceed 30 cm.

10. The method of use according to claim 8, characterized in that: In the third stage described in step (3), the plant seeds are 5-6% of Chinese herbs and 94-95% of shrubs.

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